Ron,
My rearview camera is just like Lance's, except white... In his first photo the microphone is visible. There are a part of wires on the left edge of the camera face he is holding in his hand.
So,,,, if you have the same original camera as us, there's your microphone. And while on the topic I wondered why I heard nothing from the camera as well. I discovered that the camera has a microphone, but the wire (and RCA plug) for the sound stops under the dashboard. It was never routed to my overhead display.
I put it on my to do list to one day finish what phoenix should have connected... LOL... Just one more thing to do.
Larry